Dynamical Dark Matter from strongly-coupled dark sectors

Abstract

Dynamical Dark Matter (DDM) is an alternative framework for dark-matter physics in which the dark sector comprises a vast ensemble of particle species whose Standard-Model decay widths are balanced against their cosmological abundances. Previous studies of this framework have focused on a particular class of DDM ensembles-motivated primarily by Kaluza-Klein towers in theories with extra dimensions-in which the density of dark states scales roughly as a polynomial of the mass. In this paper, by contrast, we study the properties of a different class of DDM ensembles in which the density of dark states grows exponentially with mass. Ensembles with this Hagedorn-like property arise naturally as the "hadronic" resonances associated with the confining phase of a strongly-coupled dark sector; they also arise naturally as the gauge-neutral bulk states of Type I string theories. We study the dynamical properties of such ensembles, and demonstrate that an appropriate DDM-like balancing between decay widths and abundances can emerge naturally-even with an exponentially rising density of states. We also study the effective equations of state for such ensembles, and investigate some of the model-independent observational constraints on such ensembles that follow directly from these equations of state. In general, we find that such constraints tend to introduce correlations between various properties of these DDM ensembles such as their associated mass scales, lifetimes, and abundance distributions. For example, we find that these constraints allow DDM ensembles with energy scales ranging from the GeV scale all the way to the Planck scale, but that the total present-day cosmological abundance of the dark sector must be spread across an increasing number of different states in the ensemble as these energy scales are dialed from the Planck scale down to the GeV scale. Numerous other correlations and constraints are also discussed.

Ultraviolet completion of a composite asymmetric dark matter model with a dark photon portal

“…The dark higgsino φ D can decay into the dark electron, the slepton, and the MSSM Higgs doublet through the SUSY version of Eq. (26). This decay process occurs faster than the decay through the kinetic mixing if the sleptons have the mass of the order of TeV.…”

“…As in the case with a non-SUSY model, we simply assume that the dark electron chiral multiplet gets a mass of the order of the dark GUT scale in order to stabilize the dark neutron, and thus we omit the term like Eq. (26). Due to superpartners of dark fermions, the portal interaction arises at dimension six rather than dimension seven.…”

Boxes, boosts, and energy duality: Understanding the Galactic Center gamma-ray excess through Dynamical Dark Matter

“…We assume that each χ n has a relic abundance Ω n such that the ensemble as a whole carries the observed total darkmatter relic abundance. Indeed, such DDM ensembles are realized in various well-motivated physics models beyond the SM, including scenarios with extra spacetime dimensions [42,43,57], confining hidden-sector gauge groups [58], large spontaneously broken symmetry groups [59,60], and even certain string configurations [58,61].…”

“…DDM models do not merely have a random assortment of dark-matter componentsthese components must also have properties such as masses, abundances, and decay widths which obey specific scaling relations. These scaling relations emerge naturally from a variety of underlying DDM constructions [42,43,[57][58][59][60]. The question that remains, then, is not merely whether there exists a nontrivial intermediary injection spectrum dN ϕ =dE ϕ that can fit the GC excess, but whether this injection spectrum is also consistent with an underlying dark sector whose individual components exhibit scaling relations of the sort DDM assumes.…”

Dark matter and naturalness

“…However, a dark sector (or "hidden sector") may provide the dark matter of our universe, which will be the focus of this paper (e.g., see Refs. [3][4][5][6][7][8][9][10][11][12][13][14][15]). So could it be that the parameters of the dark sector also conspire to be fine-tuned simply for life to exist; namely that the gravitational interaction between the dark and visible sectors (or other possible weak interactions) are not too large or small as to make it difficult for galaxies, stars, etc to form?…”